Lecture Notes: Interior Waterproofing and Drainage Solutions

Introduction

• Addressing water and drainage on the interior of masonry foundation walls.
• Importance in cases where exterior excavation isn’t possible.

Interior Drainage System

Dimple Mat Membrane

• Installed against the interior side of masonry walls.
• Provides drainage space and capillary break.
• Acts as a vapor barrier when seams are taped.
• Prevents efflorescence (chalky white substance) and spalling (pieces falling off) by maintaining 100% humidity in the gap.

Interior Drainage Tile

• Placed in a crushed stone bed, wrapped with filter fabric.
• Discharges water to sump pumps with backup batteries.
• Drains water leaking through masonry walls.

Osmotic Pressure & Salt Buildup

• Water carries dissolved salts, leading to evaporation on interior walls.
• Salt deposits can damage walls causing efflorescence and spalling.
• Efflorescence: visible salt deposits.
• Subfluorescence: salt deposits within masonry causing pressure.

Concrete Slab & Epoxy Vapor Barrier

• Excavated portion patched and covered with a fluid-applied epoxy barrier.
• Prevents liquid water, vapor migration, and radon intrusion.

Insulation

• Closed-cell polyurethane spray foam: high R-value per inch, air barrier, vapor retarder.
• Additional insulation with mineral wool-batt between 2x4 framing.
• Flexible design and insulation due to dimple mat.

Exterior Measures

Correcting Grading

• Slope away from foundation walls to limit surface water.

French Drain System

• Installed around the foundation perimeter near the surface.
• Not reaching down to footings but aiding surface water drainage.
• Capped with impervious pavers or impermeable soil cap.

Stone Foundation Example

• Similar approach with dimple mat membrane and perimeter drain tile.
• Epoxy vapor barrier over excavated concrete slab.
• Grading and French drain system to direct water away.

Additional Resources

• A Guide to Moisture Management for Residential Remodels: eBook for more solutions.
• Website: Over 150 free building science articles.

Conclusion

• Importance of understanding moisture management before remodel projects.
• Reference eBook and articles for detailed solutions.

Good luck with your projects!